Donald Trump’s long-awaited vice president announcement is getting closer, say sources, as the Republican National Convention on July 18 quickly approaches.

There are reports that New Jersey Gov. Chris Christie and former House Speaker Newt Gingrich are at the top of the VP shortlist and currently filling out paperwork for the vetting process. Other names include Alabama Sen. Jeff Sessions, Tennessee Sen. Bob Corker, and Indiana Gov. Mike Pence.

The intense speculation around Trump’s potential running mate speaks to the high salience VP picks have had in previous election years. Vice presidential picks often serve as a unifying force for a party after a divisive contest for the nomination, a point Trump is likely considering as he tries to woo establishment Republicans onto his side. The right VP candidate could help bring party leaders, Republican voters, and big donors into the Trump fold, all people the campaign desperately needs ahead of the general election.

“Even if it doesn’t move the needle much, the vice presidential selection can help compensate for some of the problems and concerns that voters have about a nominee,” Julian Zelizer, a professor of history and public affairs at Princeton University, writes for CNN. “In Trump’s case this is especially important given how unprecedented and unpredictable his candidacy is.”

The assumed VP frontrunners, Governor Christie and former Representative Gingrich, could help Trump work the legislative aspect of the presidency.

Gingrich has the experience. During his 20 years as a representative from Georgia, Gingrich served as House minority whip for six years and speaker for four. And Christie, who was appointed as US Attorney for the District of New Jersey by President George W. Bush in 2002 before becoming governor in 2010, has been crucial to the Trump campaign, shopping around for endorsements and donations.

“[Trump] is the first to admit that he doesn’t know all the ways of Washington,” Robert Jeffress, a Dallas pastor who has been close with Trump during his campaign, told The Washington Post. “So to actually push what he wants through, he’s willing to reach out and get somebody to lend a hand.”

With more than 60 percent of voters feeling unfavorable about Trump at the end of June, the right VP pick could help voters feel more positive about the Republican ticket.

However, Gingrich and Christie might not be the ones to do it.

When Gingrich withdrew from the presidential race in 2012, he had unfavorable ratings ranging between 56 and 67 percent. And even before his unsuccessful presidential bid, Gingrich had a less-than-perfect track record, as John Pitney Jr. explains:

Trump might be thinking that Gingrich could be his link to the Washington establishment that he has so long criticized. If so, he should think again. During his speakership, Gingrich alienated his colleagues through his impetuous leadership style. There was an abortive GOP effort to depose him in 1997, and in the following year, colleagues finally forced him to leave after the Clinton impeachment backfired politically. During his presidential race, few lawmakers endorsed him.

And Christie, who once seemed like a presidential contender himself, may not be that much better.

Christie’s approval ratings in his home state have tanked since he started supporting Trump. Regardless of age, gender, or education, 60 to 68 percent of New Jersey voters disapproved of Christie in May, the lowest rating ever for the governor. And when asked what they think of a VP role on Trump’s ticket, 72 percent of New Jersey voters said they disapprove.

“It’s a drastic decline in popularity for a governor who once looked like a strong choice for president,” Maurice Carroll, assistant director for Quinnipiac University Poll, said in a press release last month. “Christie-for-President was a flop, and, as far as the local folks are concerned, so is Christie-for-Vice President. Forget local pride, New Jersey voters say overwhelmingly; they don’t want their gov on a Trump ticket.”